In recent years, a technique referred to as OpenFlow is proposed (see Non-Patent Document 1). In OpenFlow, communication is deemed as an end-to-end flow, and routing control, failure recovery, load distribution, and optimization are executed for each flow. FIG. 18 is a conceptual diagram of an OpenFlow switch. The OpenFlow switch, which serves as a forwarding node, includes a secure channel for communication with an OpenFlow controller serving as a control apparatus. The OpenFlow switch operates in accordance with a flow table appropriately added or rewritten by the OpenFlow controller. In the flow table, a group of: matching rules (header fields) matched against packet headers; actions defining process contents; and flow statistics information (counters) is defined for each flow (see FIGS. 19 and 20).
FIG. 21 illustrates action names and action contents defined in Non-Patent Document 2. OUTPUT is an action for outputting data to a specified port (interface). SET_VLAN_VID to SET_TP_DST are actions for modifying packet header fields.
For example, upon receiving a packet, the OpenFlow switch searches the flow table for an entry having matching rules (see header fields in FIGS. 19 and 20) that match header information of the received packet. As a result of the search, if an entry matching the received packet is found, the OpenFlow switch executes process contents described in action fields of the entry on the received packet. If, as a result of the search, no entry matching the received packet is found, the OpenFlow switch forwards the received packet to the OpenFlow controller via the secure channel to request the OpenFlow controller to determine a packet route based on the source/destination of the received packet. Upon receiving a flow entry realizing the route, the OpenFlow switch updates the flow table. In this way, the OpenFlow switch uses an entry stored in the flow table as a process rule to forward a packet.    Non-Patent Document 1: Nick McKeown and seven others, “OpenFlow: Enabling Innovation in Campus Networks”, [online], searched on Dec. 22, 2009, Internet <URL:http://www.openflowswitch.org//documents/openflow-wp-latest.pdf>    Non-Patent Document 2: “OpenFlow Switch Specification” Version 0.9.0. (Wire Protocol 0x98), searched on Dec. 22, 2009, Internet <URL:http://www.openflowswitch.org/documents/openflow-spec-v0.9.0.pdf>